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How to Reduce Black Smoke in Diesel Engines & Determine The Root Causes

October 30, 2016 | Engine Info

Diesel engines have a bad reputation when it comes to emissions and cleanliness. The large diesel trucks spewing out large amounts of black smoke (rolling coal as they say) have always been frowned upon, and with the recent scandals involving lots of diesel engines from famous manufacturers even diesel cars are beginning to be on the receiving end of a lot of hate. However, the fact of the matter is that diesels aren’t as bad as most people make them up to be. Just because there’s black smoke exiting the exhaust doesn’t mean diesel is any more harmful to the environment. What people don’t realize is that all internal combustion engines, even petrol ones emit lots of emissions, we just can’t see them. Placed under a UV/infrared camera, you’ll be able to notice this.

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Still, it’s not normal for any diesel vehicle to be chucking out large amounts of black smoke. New, common-rail diesels are a massive improvement over the older diesels and rarely emit any smoke from the exhaust. If they do however, it’s because there’s a defect and it needs to be addressed in the shortest time possible. It isn’t just bad for the environment, but bad for your wallet. Black smoke equals less mpg and ultimately, more money wasted on fuel. Below are some causes and some tips on how to reduce black smoke in your car which are using diesel engine.

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Check injector condition

Look at the fuel delivery system. Try the simpler stuff first. Go over the injector timing and the EGR system. If there’s an issue with it, an EGR valve may need to be replaced. If that doesn’t fix it, it’s most probably a mechanical issue. Check the injectors. It’s possible that they’re clogged up or that they simply need to be replaced. Wrong valve clearances have been known to give the same problems, but that’s uncommon.

Restricted Air: Check air filter condition

Black smoke exiting the exhaust means one thing: the fuel is only partially-burned fuel. A normal engine burns all of its fuel, giving out water and CO2. Black smoke indicates that something is causing the fuel to only burn partially. Because diesel fuel is only part of the mixture in the combustion process, we have to take a look at the other one: air. If there’s not enough air getting through to the engine, the mixture will be too rich, i.e. the ratio will favor the fuel. Check the air filter for starters, and replace it if it’s dirty. If there’s not enough air getting in you’ve found your culprit.

Engine Deposits: Add a detergent additive regularly

If your car is older and has more miles on it, it could very well be that it’s simply accumulated a lot of combustion product in critical areas resulting in less than ideal functioning. Because diesels run for longer and the fact that diesel is crude fuel, with no detergents from the refinery, diesel engines are prone to deposits. The fix in most cases is easy. Add a detergent additive to your diesel fuel, and do it on a regular basis.

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